In 9.5 and master there is no need to support legacy truncation. This is
just committed separately to make it easier to backpatch the WAL logged
multixact truncation to 9.3 and 9.4 if we later decide to do so.

I bumped master's magic from 0xD086 to 0xD088 and 9.5's from 0xD085 to
0xD087 to avoid 9.5 reusing a value that has been in use on master while
keeping the numbers increasing between major versions.

Discussion: 20150621192409.GA4797@alap3.anarazel.de
Backpatch: 9.5

The fact that multixact truncations are not WAL logged has caused a fair
share of problems. Amongst others it requires to do computations during
recovery while the database is not in a consistent state, delaying
truncations till checkpoints, and handling members being truncated, but
offset not.

We tried to put bandaids on lots of these issues over the last years,
but it seems time to change course. Thus this patch introduces WAL
logging for multixact truncations.

This allows:
1) to perform the truncation directly during VACUUM, instead of delaying it
   to the checkpoint.
2) to avoid looking at the offsets SLRU for truncation during recovery,
   we can just use the master's values.
3) simplify a fair amount of logic to keep in memory limits straight,
   this has gotten much easier

During the course of fixing this a bunch of additional bugs had to be
fixed:
1) Data was not purged from memory the member's SLRU before deleting
   segments. This happened to be hard or impossible to hit due to the
   interlock between checkpoints and truncation.
2) find_multixact_start() relied on SimpleLruDoesPhysicalPageExist - but
   that doesn't work for offsets that haven't yet been flushed to
   disk. Add code to flush the SLRUs to fix. Not pretty, but it feels
   slightly safer to only make decisions based on actual on-disk state.
3) find_multixact_start() could be called concurrently with a truncation
   and thus fail. Via SetOffsetVacuumLimit() that could lead to a round
   of emergency vacuuming. The problem remains in
   pg_get_multixact_members(), but that's quite harmless.

For now this is going to only get applied to 9.5+, leaving the issues in
the older branches in place. It is quite possible that we need to
backpatch at a later point though.

For the case this gets backpatched we need to handle that an updated
standby may be replaying WAL from a not-yet upgraded primary. We have to
recognize that situation and use "old style" truncation (i.e. looking at
the SLRUs) during WAL replay. In contrast to before, this now happens in
the startup process, when replaying a checkpoint record, instead of the
checkpointer. Doing truncation in the restartpoint is incorrect, they
can happen much later than the original checkpoint, thereby leading to
wraparound.  To avoid "multixact_redo: unknown op code 48" errors
standbys would have to be upgraded before primaries.

A later patch will bump the WAL page magic, and remove the legacy
truncation codepaths. Legacy truncation support is just included to make
a possible future backpatch easier.

Discussion: 20150621192409.GA4797@alap3.anarazel.de
Reviewed-By: Robert Haas, Alvaro Herrera, Thomas Munro
Backpatch: 9.5 for now

This replaces ill-fated commit 5ddc7288,
which was reverted because it broke active uses of FK cache entries.  In
this patch, we still do nothing more to invalidatable cache entries than
mark them as needing revalidation, so we won't break active uses.  To keep
down the overhead of InvalidateConstraintCacheCallBack(), keep a list of
just the currently-valid cache entries.  (The entries are large enough that
some added space for list links doesn't seem like a big problem.)  This
would still be O(N^2) when there are many valid entries, though, so when
the list gets too long, just force the "sinval reset" behavior to remove
everything from the list.  I set the threshold at 1000 entries, somewhat
arbitrarily.  Possibly that could be fine-tuned later.  Another item for
future study is whether it's worth adding reference counting so that we
could safely remove invalidated entries.  As-is, problem cases are likely
to end up with large and mostly invalid FK caches.

Like the previous attempt, backpatch to 9.3.

Jan Wieck and Tom Lane

(Third time's the charm, I hope.)

Additional testing disclosed that this code could mangle already-localized
output from the "money" datatype.  We can't very easily skip applying it
to "money" values, because the logic is tied to column right-justification
and people expect "money" output to be right-justified.  Short of
decoupling that, we can fix it in what should be a safe enough way by
testing to make sure the string doesn't contain any characters that would
not be expected in plain numeric output.

On closer inspection, those seemingly redundant atoi() calls were not so
much inefficient as just plain wrong: the author of this code either had
not read, or had not understood, the POSIX specification for localeconv().
The grouping field is *not* a textual digit string but separate integers
encoded as chars.

We'll follow the existing code as well as the backend's cash.c in only
honoring the first group width, but let's at least honor it correctly.

This doesn't actually result in any behavioral change in any of the
locales I have installed on my Linux box, which may explain why nobody's
complained; grouping width 3 is close enough to universal that it's barely
worth considering other cases.  Still, wrong is wrong, so back-patch.

This code did the wrong thing entirely for numbers with an exponent
but no decimal point (e.g., '1e6'), as reported by Jeff Janes in
bug #13636.  More generally, it made lots of unverified assumptions
about what the input string could possibly look like.  Rearrange so
that it only fools with leading digits that it's directly verified
are there, and an immediately adjacent decimal point.  While at it,
get rid of some useless inefficiencies, like converting the grouping
count string to integer over and over (and over).

This has been broken for a long time, so back-patch to all supported
branches.

Previously, a function call appearing at the top level of WHERE had a
hard-wired selectivity estimate of 0.3333333, a kludge conveniently dated
in the source code itself to July 1992.  The expectation at the time was
that somebody would soon implement estimator support functions analogous
to those for operators; but no such code has appeared, nor does it seem
likely to in the near future.  We do have an alternative solution though,
at least for immutable functions on single relations: creating an
expression index on the function call will allow ANALYZE to gather stats
about the function's selectivity.  But the code in clause_selectivity()
failed to make use of such data even if it exists.

Refactor so that that will happen.  I chose to make it try this technique
for any clause type for which clause_selectivity() doesn't have a special
case, not just functions.  To avoid adding unnecessary overhead in the
common case where we don't learn anything new, make selfuncs.c provide an
API that hooks directly to examine_variable() and then var_eq_const(),
rather than the previous coding which laboriously constructed an OpExpr
only so that it could be expensively deconstructed again.

I preserved the behavior that the default estimate for a function call
is 0.3333333.  (For any other expression node type, it's 0.5, as before.)
I had originally thought to make the default be 0.5 across the board, but
changing a default estimate that's survived for twenty-three years seems
like something not to do without a lot more testing than I care to put
into it right now.

Per a complaint from Jehan-Guillaume de Rorthais.  Back-patch into 9.5,
but not further, at least for the moment.

If we have a local Var of say varchar type with default collation, and
we apply a RelabelType to convert that to text with default collation, we
don't want to consider that as creating an FDW_COLLATE_UNSAFE situation.
It should be okay to compare that to a remote Var, so long as the remote
Var determines the comparison collation.  (When we actually ship such an
expression to the remote side, the local Var would become a Param with
default collation, meaning the remote Var would in fact control the
comparison collation, because non-default implicit collation overrides
default implicit collation in parse_collate.c.)  To fix, be more precise
about what FDW_COLLATE_NONE means: it applies either to a noncollatable
data type or to a collatable type with default collation, if that collation
can't be traced to a remote Var.  (When it can, FDW_COLLATE_SAFE is
appropriate.)  We were essentially using that interpretation already at
the Var/Const/Param level, but we weren't bubbling it up properly.

An alternative fix would be to introduce a separate FDW_COLLATE_DEFAULT
value to describe the second situation, but that would add more code
without changing the actual behavior, so it didn't seem worthwhile.

Also, since we're clarifying the rule to be that we care about whether
operator/function input collations match, there seems no need to fail
immediately upon seeing a Const/Param/non-foreign-Var with nondefault
collation.  We only have to reject if it appears in a collation-sensitive
context (for example, "var IS NOT NULL" is perfectly safe from a collation
standpoint, whatever collation the var has).  So just set the state to
UNSAFE rather than failing immediately.

Per report from Jeevan Chalke.  This essentially corrects some sloppy
thinking in commit ed3ddf91, so back-patch
to 9.3 where that logic appeared.

The comments here stated that this was just in case we ever had an
ALTER OPERATOR command that could remap an operator to a different
function.  But those comments have been here for a long time, and no
such command has come about.  In the absence of such a feature,
forcing the pg_proc OID to be looked up again each time we reread a
stored rule or similar is just a waste of cycles.  Moreover, parallel
query needs a way to reread the exact same node tree that was written
out, not one that has been slightly stomped on.  So just get rid of
this for now.

Per discussion with Tom Lane.

Previously pg_controldata didn't report newestCommitTs and this was
an oversight in commit 73c986ad.

Also this patch changes pg_resetxlog so that it uses the same sentences
as pg_controldata does, regarding oldestCommitTs and newestCommitTs,
for the sake of consistency.

Back-patch to 9.5 where track_commit_timestamp was added.

Euler Taveira

The old minimum values are rather large, making it time consuming to
test related behaviour. Additionally the current limits, especially for
multixacts, can be problematic in space-constrained systems. 10000000
multixacts can contain a lot of members.

Since there's no good reason for the current limits, lower them a good
bit. Setting them to 0 would be a bad idea, triggering endless vacuums,
so still retain a limit.

While at it fix autovacuum_multixact_freeze_max_age to refer to
multixact.c instead of varsup.c.

Reviewed-By: Robert Haas
Discussion: CA+TgmoYmQPHcrc3GSs7vwvrbTkbcGD9Gik=OztbDGGrovkkEzQ@mail.gmail.com
Backpatch: back to 9.0 (in parts)

Previously, ANALYZE simply ignored columns of datatypes that have neither
a btree nor hash opclass (which means they have no recognized equality
operator).  Without a notion of equality, we can't identify most-common
values nor estimate the number of distinct values.  But we can still
count nulls and compute the average physical column width, and those
stats might be of value.  Moreover there are some tools out there that
don't work so well if rows are missing from pg_statistic.  So let's
add suitable logic for this case.

While this is arguably a bug fix, it also has the potential to change
query plans, and the gain seems not worth taking a risk of that in
stable branches.  So back-patch into 9.5 but not further.

Oleksandr Shulgin, rewritten a bit by me.

For parallel query, we need to be able to pass a Plan to a worker, so
that it knows what it's supposed to do.  We could invent our own way
of serializing plans for that purpose, but piggybacking on the
existing node infrastructure seems like a much better idea.

Initially, we'll probably only support a limited number of nodes
within parallel workers, but this commit adds support for everything
in plannodes.h except CustomScan, because doing it all at once seems
easier than doing it piecemeal, and it makes testing this code easier,
too.  CustomScan is excluded because making that work requires a
larger rework of that facility.

Amit Kapila, reviewed and slightly revised by me.

It's declared as being an array of bool, but it's printed
differently from the way bool and arrays of bool are handled
elsewhere.

Patch by Amit Kapila.  Anomaly noted independently by Amit Kapila
and KaiGai Kohei.

Commit e9568083 introduces adding pages
to FSM for ordinary insert, but autoanalyze was able just cleanup
pending list without adding to FSM.

Also fix double call of IndexFreeSpaceMapVacuum() during ginvacuumcleanup()

Report from Fujii Masao
Patch by me
Review by Jeff Janes

This logic was missing from ExplainPreScanNode, from which I derived
planstate_tree_walker.  But it shouldn't be missing, especially not
from a generic walker function, so add it.

KaiGai Kohei

Per bug #13631 from KOIZUMI Satoru.

A bunch of tests missed specifying that empty transactions shouldn't be
displayed. That causes problems when e.g. autovacuum runs in an
unfortunate moment. The tests in question only run for a very short
time, making this quite unlikely.

Reported-By: Buildfarm member axolotl
Backpatch: 9.4, where logical decoding was introduced

The previous wrong value lead to wrong LOCK_DEBUG output, never showing
any shared lock holders.

Reported-By: Alexander Korotkov
Discussion: CAPpHfdsPmWqz9FB0AnxJrwp1=KLF0n=-iB+QvR0Q8GSmpFVdUQ@mail.gmail.com
Backpatch: 9.5, where the bug was introduced.

This deserves to be greatly expanded and improved, but it's a start.

Discussion: 20150827145219.GI2435@awork2.anarazel.de

Based on patch by Thomas Munro <thomas.munro@enterprisedb.com>, although
I rephrased most of the initial work.

mul_var() postpones propagating carries until it risks overflow in its
internal digit array.  However, the logic failed to account for the
possibility of overflow in the carry propagation step, allowing wrong
results to be generated in corner cases.  We must slightly reduce the
when-to-propagate-carries threshold to avoid that.

Discovered and fixed by Dean Rasheed, with small adjustments by me.

This has been wrong since commit d72f6c75,
so back-patch to all supported branches.

This commit's parent made superfluous the bit's sole usage.  Referential
integrity checks have long run as the subject table's owner, and that
now implies RLS bypass.  Safe use of the bit was tricky, requiring
strict control over the SQL expressions evaluating therein.  Back-patch
to 9.5, where the bit was introduced.

Based on a patch by Stephen Frost.

Every query of a single ENABLE ROW SECURITY table has two meanings, with
the row_security GUC selecting between them.  With row_security=force
available, every function author would have been advised to either set
the GUC locally or test both meanings.  Non-compliance would have
threatened reliability and, for SECURITY DEFINER functions, security.
Authors already face an obligation to account for search_path, and we
should not mimic that example.  With this change, only BYPASSRLS roles
need exercise the aforementioned care.  Back-patch to 9.5, where the
row_security GUC was introduced.

Since this narrows the domain of pg_db_role_setting.setconfig and
pg_proc.proconfig, one might bump catversion.  A row_security=force
setting in one of those columns will elicit a clear message, so don't.

Per Coverity.  Back-patch to 9.0 (all supported versions).

Michael Paquier, reviewed (in earlier versions) by Heikki Linnakangas.

RemoveLocalLock() must consider the possibility that LockAcquireExtended()
failed to palloc the initial space for a locallock's lockOwners array.
I had evidently meant to cope with this hazard when the code was originally
written (commit 1785aceb), but missed that
the pfree needed to be protected with an if-test.  Just to make sure things
are left in a clean state, reset numLockOwners as well.

Per low-memory testing by Andreas Seltenreich.  Back-patch to all supported
branches.

BSD find is not very smart and ends up writing double slashes into the
output in those cases.  Also, xgettext is not very smart and splits the
file names incorrectly in those cases, resulting in slightly incorrect
file names being written into the POT file.

The shm_mq mechanism was built to send error (and notice) messages and
tuples between backends.  However, shm_mq itself only deals in raw
bytes.  Since commit 2bd9e412, we have
had infrastructure for one message to redirect protocol messages to a
queue and for another backend to parse them and do useful things with
them.  This commit introduces a somewhat analogous facility for tuples
by adding a new type of DestReceiver, DestTupleQueue, which writes
each tuple generated by a query into a shm_mq, and a new
TupleQueueFunnel facility which reads raw tuples out of the queue and
reconstructs the HeapTuple format expected by the executor.

The TupleQueueFunnel abstraction supports reading from multiple tuple
streams at the same time, but only in round-robin fashion.  Someone
could imaginably want other policies, but this should be good enough
to meet our short-term needs related to parallel query, and we can
always extend it later.

This also makes one minor addition to the shm_mq API that didn'
seem worth breaking out as a separate patch.

Extracted from Amit Kapila's parallel sequential scan patch.  This
code was originally written by me, and then it was revised by Amit,
and then it was revised some more by me.

These functions have been looking up type info for every row they
process. Instead of doing that we only look them up the first time
through and stash the information in the aggregate state object.

Affects json_agg, json_object_agg, jsonb_agg and jsonb_object_agg.

There is plenty more work to do in making these more efficient,
especially the jsonb functions, but this is a virtually cost free
improvement that can be done right away.

Backpatch to 9.5 where the jsonb variants were introduced.

After an internal failure in shortest() or longest() while pinning down the
exact location of a match, find() forgot to free the DFA structure before
returning.  This is pretty unlikely to occur, since we just successfully
ran the "search" variant of the DFA; but it could happen, and it would
result in a session-lifespan memory leak since this code uses malloc()
directly.  Problem seems to have been aboriginal in Spencer's library,
so back-patch all the way.

In passing, correct a thinko in a comment I added awhile back about the
meaning of the "ntree" field.

I happened across these issues while comparing our code to Tcl's version
of the library.

Report from Peter Eisentraut

Use IsBinaryCoercible() method instead of custom
is_expected_type/is_text_type functions which was introduced when tsearch2
was moved into core.

Per report by David E. Wheeler
Analysis by Tom Lane
Patch by me

This setting contains extra configuration for the temp instance, as used
in pg_regress' --temp-config flag.

Backpatch to 9.2 where test.sh was introduced.

ExplainPreScanNode knows how to iterate over a generic tree of plan
states; factor that logic out into a separate walker function so that
other code, such as upcoming patches for parallel query, can also use
it.

Patch by me, reviewed by Tom Lane.

Back in the day this did not work, but modern compilers should handle it themselves.